The present invention relates to a touch panel and a production method thereof, in particular, to a configuration and a production method of a capacitive touch panel.
Recently, the use of a touch panel which is used in combination with a display device such as a liquid crystal display device for an input operation to an electronic device through contact with a screen has been spreading in various electronic devices including portable information equipment, vending machines, automated teller machines and gaming devices.
The touch panel is categorized into several types including resistive film type, capacitive type, infrared type, ultrasonic type and electromagnetic-induction coupling type, depending on the operating principle thereof. Among those, the touch panel of the capacitive type having a high transmittance and excellent durability has been particularly attracting attention.
An example of the touch panel as illustrated in FIG. 12 is disclosed by JP 2013-117816 A. The touch panel includes a plurality of first sensor electrode arrays 2 extending along a first direction D1 and arranged parallel to one another in a second direction D2 that crosses the first direction D1, and a plurality of second sensor electrode arrays 3 extending along the second direction D2 and arranged parallel to one another in the first direction D1 on a transparent substrate 1. Each of the first sensor electrode arrays 2 is consisted of a plurality of rhombic island-shaped electrode portions 5 connected to one another along the first direction D1 through linear portions 4, and each of the second sensor electrode arrays 3 is consisted of a plurality of rhombic island-shaped electrode portions 7 connected to one another along the second direction D2 through bridge portions 6. Having the linear portions 4 respectively superimposed on the bridge portions 6 with a distance therebetween in the thickness direction of the transparent substrate 1, the first sensor electrode arrays 2 and the second sensor electrode arrays 3 cross each other in a non-contact state. The first sensor electrode arrays 2 and the second sensor electrode arrays 3 are made of a transparent conductor and are arranged in an active area A on the transparent substrate 1.
An end of a lead-out wiring portion 8 is connected to an end of each of the first sensor electrode arrays 2, and another end of the lead-out wiring portion 8 extends to an edge portion of the transparent substrate 1 to be connected to a terminal 8A. Similarly, an end of a lead-out wiring portion 9 is connected to an end of each of the second sensor electrode arrays 3, and another end of the lead-out wiring portion 9 extends to another edge portion of the transparent substrate 1 to be connected to a terminal 9A. The lead-out wiring portions 8 and 9 are formed of a metal having an excellent conductivity so as to keep the electric resistance value low, and are arranged in a non-active area B outside of the active area A.
In addition, surfaces of the active area A and the non-active area B are covered by a transparent protection layer 10.
The touch panel of JP 2013-117816 A is used as being superimposed on a screen of a display device. An image is displayed by the display device through the plurality of first sensor electrode arrays 2 and the plurality of second sensor electrode arrays 3 that are formed of a transparent conductor and arranged in the active area A. When an arbitrary portion on the protection layer 10 in the active area A is touched, change in capacitance at the portion is detected through the lead-out wiring portions 8 and 9, whereby it becomes possible to detect the touched position, to switch between on and off, and the like.
The lead-out wiring portions 8 and 9 however are formed of a metal and thus cannot transmit light. Hence, in general, the non-active area B where the lead-out wiring portions 8 and 9 are arranged cannot be used as a display region and is masked.
Accordingly, when a display device is designed such that an entire screen thereof is the active area A of a touch panel, the touch panel becomes larger than the screen of the display device by the portion of the non-active area B around the active area A. In addition, when a touch panel of the same size as that of the screen of the display device is disposed, the display region of the display device in use has to be limited by the portion of the non-active area B.
In particular, screens of recent electronic devices have been increasing in size. When the active area A is enlarged to increase the screen size while the sizes of the respective island-shaped electrodes 5 and 7 are maintained, i.e., the sensitivity of the touch panel is maintained, the number of island-shaped electrodes has to be increased, thereby requiring a greater number of lead-out wiring portions 8 and 9. As a result, the non-active area B becomes larger, increasing the influence of masking the non-active area B.
If, when the first sensor electrode arrays 2 and the second sensor electrode arrays 3 are formed on the transparent substrate 1, the lead-out wiring portions 8 and 9 are simultaneously formed by using the same transparent conductor as that forming the first sensor electrode arrays 2 and the second sensor electrode arrays 3, the lead-out wiring portions 8 and 9 are made to be transparent, whereby need of masking the non-active area B is removed. Since a typical material used for the transparent electrode such as Indium Tin Oxide (ITO) however has a higher electric resistivity than a metal wiring, it would become difficult to sensitively detect a change in capacitance.